As I have become more and more interested in trying out IR photography, I have come to wonder why companies such as Canon don't make a model of their bodies ---let's say an XSi IR ----- specifically for IR. As I understand it, one simply has to place the Hoya R-72 filter inside the body itself and we would be "good to go". Is it primarily a question of not having such a big market for IR? But wouldn't it be the case that there is no such market at the SLR level precisely because it is so difficult to use them for this purpose (using the external R-72 filter requires ultra-long ( i.e. very noisy) exposure times)? I know there are "converter" services such as Life pixels, but I wonder why it wouldn't be much easier to have an IR camera from the start. Hope this is the kind of question to be posted in this forum.

To address the point about the R-72 filter. It is not just a case of adding an external filter, the internal deep red filter must be removed and the autofocus must be retuned. Amongst the astrophotography community, the modified 40D is very porpular. Astrophotographers typically need sensitivity in the deep red end of the spectrum to photograph deep space objects. Because the work in dim light (exposures of 45 minutes are not uncommon) the live view feature is used for focussing purposes. So there is a market that Hutech have recognised. Modified cameras do cost more than the unmodified bidies however.

Actually Canon made an EOS 20Da, especially for astrophotographers. It has extended red sensitivity (but not IR). Originally it was just marketed in Japan (where maybe astrophotography is a more popular hobby?) and even there it was "special order", but it did make it over here to the US and sold for $2200 (about $600-$800 more than a 20D at the time).